Recent progress in low power electronics and sensors, as well as suitable electronics for power harvesting, makes possible new ideas to scavenge energy from different sources. In particular, environmental mechanical vibration sources have gained much attention because of their ubiquity and the availability of new high-performance materials that can be used to convert mechanical vibrations to a suitable electrical response. Linear resonant mechanical structures, typically based on resonant structures (like for example cantilever beams) and exploiting piezoelectric, macro-fiber composites, electromagnetic or electrostatic conversion mechanisms are able to efficiently harvest energy when it is concentrated very close to their resonance frequency. However, ambient mechanical vibrations come in a large variety of forms such as induced oscillations, seismic noise, vehicle motion, acoustic noise, multi-tone vibrating systems, and, more generally, noisy environments. Occasionally, the energy to be collected may be confined to a very specific region of the frequency spectrum, but very often, however, the available (for harvesting) energy is distributed over a wide frequency spectrum, and resonant energy harvesters lose their effectiveness.
Different solutions, for increasing the operational bandwidth of linear harvesters have been proposed. Most of these solutions, however, present disadvantages including increased complexity, decrease in the power generated, the need for extra systems and energy, low efficiency, as well as difficulty in implementation. On the other hand, the exploitation of new harvesting configurations based on non-linear mechanisms, such as bi-stable systems, has the potential to outperform traditional (linear) energy harvesters under the right set of operating conditions.